Showing papers on "Fish oil published in 1992"

Dietary supplementation with fish oil in ulcerative colitis.

Abstract: ▪Objective:To determine the efficacy of fish oil supplementation in patients with active ulcerative colitis. ▪Design:Multicenter, randomized, double-blind, placebo-controlled, crossover tr...

Treatment of ulcerative colitis with fish oil supplementation: a prospective 12 month randomised controlled trial.

Abstract: The effect of fish oil on the course of ulcerative colitis was investigated in a randomised blinded controlled study. Eighty seven patients received supplements of 20 ml HiEPA fish oil as triglyceride (4.5 g of eicosapentaenoic acid) or olive oil placebo daily for one year. The oils were given in addition to standard drug therapy and trial entry was stratified for disease activity. Fish oil significantly increased the eicosapentaenoic acid content of rectal mucosa to 3.2% of total fatty acids at six months, compared with 0.63% for patients on olive oil. This was associated with increased synthesis of leukotriene B5, and 53% suppression of leukotriene B4 synthesis by ionophore--stimulated neutrophils. Leukotriene B4 suppression persisted for at least two months after treatment was stopped. Treatment with fish oil resulted in measurable, but only limited clinical benefit. For patients entering the trial in relapse (n = 53), there was a significant reduction in corticosteroid requirement after one and two months treatment. There was a trend towards achieving remission (off corticosteroids) faster in the patients on fish oil, although differences were not significant. For patients in remission at trial entry or during the trial (n = 69), there was no significant difference in the rate of relapse by log rank analysis. We conclude that fish oil supplementation produces a modest corticosteroid sparing effect in active disease, but there is no benefit in maintenance therapy.

Incorporation of n-3 fatty acids of fish oil into tissue and serum lipids of ruminants.

Abstract: This study examines the biohydrogenation and utilization of the C20 and C22 polyenoic fatty acids in ruminants. Eicosapentaenoic (20∶5n−3) and docosahexaenoic (22∶6n−3) acids were not biohydrogenated to any significant extent by rumen microorganisms, whereas C18 polyenoic fatty acids were extensively hydrogenated. The feeding of protected fish oil increased the proportion of 20∶5 from 1% to 13–18% and 22∶6 from 2% to 7–9% in serum lipids and there were reductions in the proportion of stearic (18∶0) and linoleic (18∶2) acids. The proportion of 20∶5 in muscle phospholipids (PL) increased from 1.5% to 14.7% and 22∶6 from 1.0% to 4.2%; these acids were not incorporated into muscle or adipose tissue triacylglycerols (TAG). In the total PL of muscle, the incorporated 20∶5 and 22∶6 substituted primarily for oleic (18∶1) and/or linoleic (18∶2) acid, and there was no consistent change in the porportion of arachidonic (20∶4) acid.

Dietary fat and colon cancer: Animal model studies

Abstract: Since it was first suggested that high dietary fat is a risk factor in colon cancer, there have been several studies to test this hypothesis. Epidemiologic studies suggested a positive association between dietary fat and colon cancer. Laboratory animal model studies demonstrated that not only the amount of rat, but also types of fat differing in fatty acid composition are important determining factors in colon tumor development. Chemically-induced colon tumor incidence was increased in rats fed the semipurified diets containing 23% corn oil, safflower oil, lard or beef tallow (high-fat) as compared to those fed 5% corn oil, safflower oil, lard or beef tallow diets (low-fat). Diets containing 23% conconut oil, olive oil or fish oil, or high-fat diets containing varying levels oftrans fat, had no colon tumor-enhancing effect compared to their respective low fat diets. The stage at which the effect of dietary fat is exerted appears to be mostly during the post-initiation phase of colon carcinogenesis. Lack of a colon tumor enhancing effect of dietary fish oil is observed both during the initiation and postinitiation phases. The mechanisms by which various dietary fats increase colon carcinogenesis are not fully understood. In most instances, however, the high-fat diet appears to enhance tumorigenesis through elevation of agents, such as secondary bile acids, that act as promoters of tumor development. Lack of colon tumor promotion by dietary fish oil andtrans fat appears to be mediated through their effect on mucosal ornithine decarboxylase activity, colonic secondary bile acids and/or prostaglandin synthesis.

Concentration of docosahexaenoic acid in glyceride by hydrolysis of fish oil withcandida cylindracea lipase

Abstract: In an attempt to concentrate the content of DHA (docosahexaenoic acid) in a glyceride mixture containing triglyceride, diglyceride and monoglyceride, fish oil was hydrolyzed with six kinds of microbial lipase. After the hydrolysis, free fatty acid was removed and fatty acid components of the glyceride mixtures were analyzed. When the hydrolysis withCandida cylindracea lipase was 70% complete, the DHA content in the glyceride mixture was three times more than that in the original fish oil. The EPA (eicosapentaenoic acid) content became almost 70% of the original fish oil. Hydrolysis with other lipases did not result in an increase in the DHA content in the glyceride mixtures. Hydrolysis of DHA-rich tuna oil (DHA content is about 25%) withCandida cylindracea lipase resulted in 53% DHA in the glyceride mixture. The EPA content, however, remained close to that of the original tuna oil. In this report, the acyl chain specificity of lipases is evaluated in terms of hydrolysis resistant value (HRV). HRV is the ratio between the DHA contents in the glyceride mixture of hydrolyzed oil and original oil. HRV clearly indicates differences in hydrolysis between DHA and other fatty acids (e.g., saturated and monoenoic acids).

Fish oil decreases natural resistance of mice to infection with Salmonella typhimurium.

Abstract: Mortality rate in mice fed fish oil for 4 weeks was remarkably higher after a very low peroral (PO) challenge with Salmonella typhimurium, as compared with those fed diets rich in either corn oil or hydrogenated coconut oil, or a low fat (chow) diet. None of the surviving mice fed the fish oil diet showed bacterial counts in their spleens, unlike 45.4% to 66.6% of surviving mice fed high fat or low fat diets. The spleens of mice fed fish oil presented the highest number of bacteria 7 days after intraperitoneal infection with the same bacterial strain. Thus, the current studies demonstrate that a diet rich in fish oil decreases host resistance to infection.

Effect of fish oil on the fatty acid composition of human milk and maternal and infant erythrocytes.

Abstract: To examine the effect of fish oil supplementation on the fatty acid (FA) composition of human milk and maternal and infant erythrocytes, five lactating women were supplemented with 6 g of fish oil daily for 21d. Usual maternal diets contained 1,147 mg of total n−3 FA, with 120 mg from very long-chain (>C18) n−3 FA. Supplementation increased dietary levels to 3,092 mg of total n−3 FA and 2,006 mg of very long-chain n−3 FA. Milk samples were collected daily, prior to fish oil ingestion, and at 4-h intervals on days 1, 7, 14 and 21. Milk n−3 FA content increased within 8 h and reached steady state levels within one week. The n−6 fatty acid content decreased. Erythrocyte eicosapentaenoic acid content increased from 0.24% to 1.4% (P<0.01) in mothers and from 0.11% to 0.70% (P<0.05) in infants. Docosapentaenoic acid increased from 1.4% to 2.2% (P<0.05) in mothers and from 0.30% to 0.78% (P<0.01) in infants. There was no significant change in docosahexaenoic acid or n−6 fatty acid content. Maternal platelet aggregation responses were variable. No differences in milk or plasma tocopherol levels were noted.

Effect of dietary supplementation with n-3 polyunsaturated fatty acids on physical properties and metabolism of low density lipoprotein in humans.

Abstract: The effects of marine n-3 polyunsaturated fatty acids were investigated in relation to the chemical and physical properties of low density lipoprotein (LDL) and how these changes affected LDL metabolism in humans. The subjects received supplements of six capsules daily, each capsule containing 1 g of either highly concentrated ethyl esters of n-3 fatty acids (85% eicosapentaenoic acid and docosahexaenoic acid) (n = 12) or corn oil (56% linoleic and 26% oleic acid) (n = 11). After 4 months of oil supplementation, the following changes were observed in the lipid moiety of the n-3-enriched LDL particles compared with LDL from the corn oil group: LDL cholesteryl ester, as well as the amount of total lipids of LDL, was significantly lower (0.97 +/- 0.12 versus 1.19 +/- 0.23 mg/mg protein and 1.88 +/- 0.40 versus 2.45 +/- 0.31 mg/mg, respectively; mean +/- SD, n = 6, p less than 0.05); the amount of eicosapentaenoic and docosahexaenoic acids and the unsaturation index increased (104.0 versus 29.4 micrograms/mg protein and 6.64 versus 5.49, respectively); and differential scanning calorimetry showed that LDL cholesteryl ester melting temperature was lowered by 2 degrees C (27.6 +/- 0.8 degrees versus 29.5 +/- 0.2 degrees C). The only effect observed on the protein moiety was an increase in the ratio of apolipoprotein (apo) B to cholesterol (0.66 +/- 0.17 versus 0.82 +/- 0.14 mg/mg cholesterol; p less than 0.05). Circular dichroism spectra of LDL indicated an alpha-helix content of 46 +/- 5% in apo B from both groups. No difference was observed by 13C nuclear magnetic resonance spectroscopy in the ratio of "active" to "normal" lysine residues of apo B. No detectable differences in the size of n-3 fatty acid-enriched LDL particles versus control LDL could be measured by either electron microscopy of negatively stained LDL (24.5 +/- 2.0 versus 25.0 +/- 1.5 nm) or dynamic light scattering (24.9 +/- 0.9 versus 24.9 +/- 0.4 nm). LDL from the fish oil and corn oil groups showed similar susceptibility to Cu(2+)-catalyzed lipid peroxidation, as indicated by the amount of lipid peroxides formed during the oxidation time, and degradation of oxidatively modified LDL in J774 macrophages as a function of Cu2+ oxidation time. No effect of n-3 fatty acids was observed on LDL metabolism. Specific uptake and degradation of n-3 fatty acid-enriched LDL were similar to those for control LDL in HepG2 cells as well as in human skin fibroblasts, and they showed the same ability to stimulate cholesteryl ester synthesis.(ABSTRACT TRUNCATED AT 400 WORDS)

Fat Characteristics of Pigs Fed Fish Oil Containing Eicosapentaenoic and Docosahexaenoic Acids

Abstract: Sixteen pigs averaging 81.4 kg were assigned to a control diet and three test diets containing 2, 4, or 6% fish oil. Subcutaneous fat samples from the loin were obtained by biopsy at weekly intervals and analyzed for fatty acid composition. The pigs were maintained on the diets (ad libitum access to feed) for 4 wk before slaughter at an average weight of 107.8 kg. Outer and inner layers of backfat, perirenal fat, and intermuscular fat were obtained from the carcass and analyzed for physicochemical characteristics. In the biopsy samples, the contents of eicosapen- taenoic. acid (EPA) and docosahexaenoic acid (DHA) in fat from pigs fed fish oil began to increase during the 1st wk. Rates of increase were greater during the first 2 wk than during the last 2 wk. In the carcass samples, the increase in EPA and DHA in all fat tissues analyzed became greater as the supplemental levels of fish oil were increased in the diet, whereas oleic and linoleic acids tended to be decreased by increases in EPA and DHA. Color of fat was not significantly different among the control and fish oil groups. With the increase in fish oil in the diet, the hardness of fat measured with a texturometer was decreased. The refractive index and the iodine number were increased. As for differences among anatomical locations, it was noted that EPA and DHA contents of perirenal fat were higher than those of backfat and intermuscular fat. These results indicate that porcine adipose tissues rich in EPA and DHA can be produced by feeding fish Oil.

Serum lipids, hepatic glycerolipid metabolism and peroxisomal fatty acid oxidation in rats fed omega-3 and omega-6 fatty acids.

Abstract: Rats were fed, for 3 weeks, high-fat (20% w/w) diets containing sunflower-seed oil, linseed oil or fish oil. Chow-fed rats were used as a low-fat reference. The high-fat diets markedly reduced non-fasting-rat serum triacylglycerol as compared with the low-fat reference, and the highest reduction (85%) was observed with the fish-oil group, which was significantly lower than that of the other high-fat diets. The serum concentration of phospholipids was significantly reduced (30%) only in the fish-oil-fed animals, whereas serum non-esterified fatty acids were reduced 40-50% by both the fish-oil- and linseed-oil-fed groups. The liver content of triacylglycerol showed a 1.7-fold increase with the fish-oil diet and 2-2.5-fold with the other dietary groups when compared with rats fed a low-fat diet, whereas the hepatic content of phospholipids was unchanged. Peroxisomal fatty acid oxidation (acyl-CoA oxidase) was 2-fold increased for the rats fed fish oil; however this was not significantly higher when comparison was made with rats fed the linseed-oil diet. There was no difference in phosphatidate hydrolysis (microsomal and cytosolic fractions) among animals fed the various diets. Acyl-CoA:diacylglycerol acyltransferase activity was increased by all high-fat diets, but the fish-oil-diet-fed group showed a significantly lower enzyme activity than did rats fed the other high-fat diets. A linear correlation between acyl-CoA:diacylglycerol acyltransferase activity and liver triacylglycerol was observed, and the microsomal enzyme activity was decreased 40-50% by incubation in the presence of eicosapentaenoyl-CoA. CoA derivatives of arachidonic, linolenic and linoleic acid had no inhibitory effect when compared with the control. These results indicate that dietary fish oil may have greater triacylglycerol-lowering effect than other polyunsaturated diets, owing to decreased triacylglycerol synthesis caused by inhibition of acyl-CoA:diacylglycerol acyltransferase. In addition, increased peroxisomal fatty acid oxidation and decreased availability of non-esterified fatty acids could also contribute by decreasing the amounts of fatty acids as substrates for triacylglycerol synthesis and secretion.

Dietary Fish-Oil Supplementation in Experimental Gram-Negative Infection and in Cerebral Malaria in Mice

Abstract: Dietary fish-oil supplementation interferes with eicosanoid production and appears to decrease production of interleukin-1 (IL-1) and tumor necrosis factor (TNF). The effect of fish oil was investigated in an intramuscular Klebsiella pneumoniae infection in Swiss mice and in cerebral malaria induced by Plasmodium berghei in C57B1/6 mice. After a low inoculum of K. pneumoniae, 90% of fish oil-fed mice survived; survival in control mice fed equal amounts of corn or palm oil or normal chow was 30%, 40%, and 0, respectively. Cerebral malaria occurred in only 23% of fish oil-fed mice; in the controls, cerebral malaria developed in 61%, 81%, and 78%, respectively. Contrary to what was expected, lipopolysaccharide-induced ex vivo production of IL-1 alpha and TNF alpha by peritoneal cells was significantly enhanced in fish oil-fed mice compared with controls. Indomethacin treatment did not alter the outcome in these two infections, thus arguing against reduced prostaglandin synthesis as an explanation for the increase in resistance to infection.

Effect of Six Months of Fish Oil Supplementation in Stable Rheumatoid Arthritis. A Double-blind, Controlled Study

Abstract: Therapeutic effects of fish oil (10 g/day) in rheumatoid arthritis were investigated in a randomized, controlled, double-blind study. Forty-three patients completing the study were evaluated at 0, 3 and 6 months. The nutrient intake in the fish oil group and in the control group was essentially similar. In the fish oil group, the percentage of n-3 fatty acids in serum phosphatidylcholine increased by 9.6 (range 2.6-16.1). Patients in the fish oil group reported a significantly decreased consumption of NSAID at 3 and 6 months, and the status of global arthritic activity improved at 3 months in physician's assessment. Control patients reported an increased global arthritic activity at 6 months. No change was found in patient assessment of pain, duration of morning stiffness or functional capacity. Essentially no change occurred in biochemical markers of inflammation. We conclude that fish oil has small anti-inflammatory effects with at most a NSAID-saving potential. The value of prolonged supplementation remains to be evaluated.

Decreased interleukin-1 beta levels in plasma from rheumatoid arthritis patients after dietary supplementation with n-3 polyunsaturated fatty acids.

Abstract: The effects of dietary supplementation with n-3 fatty acids on the level of cytokines and complement activation in plasma from patients with rheumatoid arthritis were examined. Thirty-two patients with active rheumatoid arthritis were included in a 12-week double-blind, randomized study of dietarynsupplementation with n-3 fatty acids (3.6 g per day) or placebo. The cytokines were measured in plasma before and after treatment with fish oil or placebo. In general, cytokine values at the upper limits of the calculated normal areas were found. The Interleukin-1 beta concentration in plasma was reduced significantly after 12 weeks of dietary supplementation with fish oil (p<0.03). No significant difference was observed in the placebo group. The tumour necrosis factor alpha activity in plasma did not change significantly (p=0.167). No significant changes were observed in the degree of complement activation. The clinical status of the patients was improved in the fish oil group, but not in the placebo group, judged by Ritchie's articular index (p<0.02). We conclude that dietary supplementation with n-3 fatty acids results in significantly reduced plasma IL-1β levels in patients with rheumatoid arthritis. Even though the cytokine levels were low, the anti-inflammatory effect of n-3 fatty acids could in part be explained by their ability to decrease cytokine production.

Composition, functionality, and sensory evaluation of eggs from hens fed dietary menhaden oil

Abstract: Enrichment of omega-3 fatty acid content of egg yolk may increase consumer acceptance of egg products if eggs maintain characteristic functionality, exhibit compositional stability, and are sensorially acceptable. The diet of laying hens was enriched with 3% menhaden oil. Arachidonic acid (20:4n-6) was decreased 70.2%, and linolenic (18:3n-3) and docosahexaenoic acid (22:6n-3) were increased 78.5% and 356%, respectively, in egg yolk. Eicosapentaenoic acid (20:5n-3) was also incorporated into test egg yolk as compared to nondetectable levels in control eggs. Cooking did not alter the fatty acid composition of eggs nor were functional properties of test eggs affected. Panelists differentiated n-3 enriched eggs from controls (P ≤ 0.01) when scrambled but not when hard cooked.

Cholestane as a digestibility marker in the absorption of polyunsaturated fatty acid ethyl esters in Atlantic salmon

Abstract: Salmonid fish require long-chain n−3 fatty acids in their diet. The digestibility of different chemical forms of fish oil fatty acids, fed as triacylglycerols, free fatty acids or ethyl esters, was examined in 300 g farmed Atlantic salmon (Salmo salar) using cholestane as an indicator of fat absorptionin lieu of the chromium oxide (Cr2O3) which is commonly used as a marker in digestibility studies. It was established that the two digestibility markers gave similar results. Conveniently, cholestane does not require a separate analysis if fatty acids are to be determined by appropriate gas-liquid chromatography. The long-chain polyunsaturated fatty acids were particularly well absorbed, the apparent digestibility being 90–98% when feeding triacylglycerols or free fatty acids. However, the digestibility of monounsaturated fatty acids (75–94%) was lower, and lower still for saturated fatty acids (50–80%). Ethyl esters of fatty acids were significantly less well absorbed (P<0.05) than were the corresponding fatty acids in free acid or triacylglycerol form. Irrespective of dietary fat type, only free fatty acids were identified in feces, indicating total hydrolysis of triacylglycerols and ethyl esters.

Lipid peroxidation products are elevated in fish oil diets even in the presence of added antioxidants.

Abstract: Purified corn and fish oil diets with different types and concentrations of antioxidants were evaluated for oxidation products In addition, a determination of different organ and carcass oxidation product levels was performed Peroxide value and thiobarbituric acid assays were performed on the diets immediately after mixing (0 h) and 24, 48 and 72 h after being fed to mice The AIN-recommended level of antioxidant addition (butylated hydroxytoluene, 002 g/100 g oil) and even the addition of 100 times this level (2 g/100 g oil), although decreasing the level of oxidation products, failed to totally prevent oxidative deterioration in diets high in fish oil Furthermore, other antioxidants added in excess to the fish oil diets also failed to completely suppress oxidative deterioration of the diets and, in addition, when fed daily to mice for a period of 4 wk, caused an accumulation of lipid peroxidation products in certain organs (eg, heart, skeletal muscle, mammary glands) and in the carcass These results provide evidence that in the preparation of fish oil diets, the addition of antioxidants at the AIN-recommended level, or even levels substantially higher, does not completely suppress oxidative deterioration of experimental diets

Antioxidant properties of individual phospholipids in a salmon oil model system

Abstract: The antioxidant properties of phospholipids (PL) in a refined salmon oil model system were measured by determining changes in the 2-thiobarbituric acid number and decreases in the ratio of docosahexaenoic acid (DHA)/palmitic acid (22:6/16:0) of a fish oil system incubated at 180°C for up to 3 h. The more phosphatidylcholine (PC) added to the oil system, the higher the oxidative stability obtained. The order of effectiveness of commercial phospholipids in inhibiting oxidation and the loss of polyunsaturated fatty acids was as follows: sphingomyelin (SPH)=lysophosphatidylcholine (LPC)=phosphatidylcholine (PC)=phosphatidylethanolamine (PE)>phosphatidylserine (PS)>phosphatidylinositol (PI)>phosphatidylglycerol (PG)>control salmon oil. Nitrogen containing PL, including PE, PC, LPC and SPH, were equally effective in exerting greater antioxidant properties than PS, PG and PI. The inverse relationship observed between the oxidation index (C22:6/C16:0) and color intensity for treatments following 2 h of heating suggests that Maillard-type reaction products may have contributed to the oxidative stability of PL-supplemented fish oils.

Changes in blood lipids and fibrinogen with a note on safety in a long term study on the effects of n-3 fatty acids in subjects receiving fish oil supplements and followed for seven years

Abstract: The present study was designed to assess the effectiveness of the n−3 fatty acids in modifying serum total, low density lipoprotein and high density lipoprotein (HDL) cholesterol, as well as serum triglycerides, over a seven-year period. Changes in plasma fibrinogen were recorded and long term safety assessed. A total of 365 subjects with ischemic heart disease (IHD), hyperlipidemia or a strong family history of IHD had their diet supplemented with MaxEPA (Seven Seas Ltd., Hull, England) fish oil containing 18–19% eicosapentaenoic acid. Venous blood samples were taken at regular intervals for lipid and fibrinogen assays and routine clinical chemistry and hematological profiling. Current medication was recorded and no further dietary modification was attempted. Triglyceride and fibrinogen were significantly reduced, whereas a significant reduction in total cholesterol occurred only in the subjects with a pre-oil level>6.5 mmol/L. HDL cholesterol significantly increased over the study period. Clinical chemistry and hematological profiles were not adversely affected, and platelet count did not change significantly. The type of lipid changes observed were those usually considered antiatherogenic. Reducing fibrinogen may result in beneficial changes in the pathological processes leading to thrombotic occlusion. The consumption of MaxEPA by our patients over a seven-year period did not indicate any adverse effects.

Effects of n -3 fatty acids on postprandial triacylglycerol and hormone concentrations in normal subjects

Abstract: The present study reports results from two investigations to determine effects of a 6-week period of moderate n-3 fatty acid supplementation (2.7 g/d) on fasting and on postprandial triacylglycerol and metabolic hormone concentrations in response to standard test meals. In the first study postprandial responses were followed for 210 min after an early morning test meal challenge; in the second study responses to an evening test meal were followed during the evening and overnight for a total period of 12 h. In both studies postprandial triacylglycerol responses to the test meals were significantly reduced after compared with before fish-oil supplementation. In the second study the triacylglycerol peak response seen between 200 and 400 min in subjects studied before supplementation with fish oils was almost completely absent in the same subjects after 6 weeks of n-3 fatty acid supplementation. Analysis of fasting concentrations of metabolites and hormones was carried out on the combined data from the two studies. There were no significant differences in total, low-density-lipoprotein- or high-density-lipoprotein-cholesterol concentrations during fish-oil supplementation, although there was considerable individual variation in cholesterol responses to the supplement. Concentrations of Apo-B and Apo-A1 were unchanged during supplementation with fish oils. Fasting and early morning postprandial GIP concentrations were lower in subjects taking fish oils, possibly due to acute effects of fish-oil capsules taken on the evening before the studies. In both studies fasting insulin and glucose and postprandial insulin concentrations remained unchanged following fish-oil supplementation. The results do not support the view that triacylglycerol-lowering effects of n-3 fatty acids are due to modulation of insulin secretion mediated via the enteroinsular axis. Further studies are required to determine the precise mechanism by which fish oils reduce both fasting and postprandial triacylglycerol concentrations.

Control of lipid oxidation in fish oil with various antioxidative compounds

Abstract: Samples of a commercial fish oil were separately treated with various chemical compounds and then studied for their susceptibility to rancidity by means of an accelerated oxidation test at 60°C.α-Tocopherol acetate and ascorbyl palmitate showed the lowest antioxidative effects among the group of seven chemicals. Anoxomer, a synthetic phenolic polymer, had an antioxidative power comparable to that of ethoxyquin, butylated hydroxytoluene or butylated hydroxyanisole when all were applied to the oil in the concentration of 0.02%. However, the most powerful antioxidant was tertiary-butylhydroquinone (TBHQ), with an antioxidant efficiency twice that of the above-mentioned phenolic compounds when used at only 0.01% concentration in the oil. Although TBHQ and Anoxomer proved to be potential compounds for preventing rancidity in fish oils, their use is still hindered by the limited acceptance from the appropriate authorities.

Effect of omega-3 fatty acids on the vascular response to angiotensin in normotensive men.

Abstract: There is a widespread interest in fish oil as a dietary supplement and possible nonpharmacologic adjunct in the treatment of hypertension. The effect of dietary fish oil on blood pressure is controversial and the effect on systemic hemodynamics and regional vascular reactivity in humans is unknown. To address these questions, a doubleblind, placebo-controlled, crossover study on the effect of dietary fish oil substitution was performed during a carefully controlled diet in 8 normotensive men. Systemic hemodynamics and the forearm vascular response to intrabrachial artery infusions of norepinephrine, phentolamine and angiotensin II were obtained. Compared with a safflower oil placebo, dietary fish oil had no effect on cardiac output (6.42 ± 0.38 vs 6.87 ± 0.28 liters/ min, p = not significant) or 24-hour blood pressure (122/68 ± 3/3 vs 122/68 ± 3/2 mm Hg, p = not significant). The vascular response to norepinephrine and phentolamine was unchanged. Fish oil, however, significantly (p

Eicosapentaenoic acid inhibits antigen-presenting cell function of murine splenocytes.

Abstract: Recently, many investigators have studied the effects of eicosapentaenoic acid (EPA)-rich fish oil on immune function and immune disease. However, effects of dietary supplementation of fish oil or EPA on the immune system are still unclear. In the present study, the effects of EPA on antigen presentation were investigated. We have used antigen-specific helper T-cell clones that proliferate in the presence of antigen [keyhole limpet haemocyanin (KLH)] and spleen cells as antigen-presenting cells (APC). Mice were divided into two groups and fed an experimental diet or a control diet for 4 weeks ad libitum. In mice fed the experimental diet, the arachidonic acid (AA) content of spleen cells was decreased and that of EPA and docosapentaenoic acid was increased markedly compared to those of the control diet. Dietary enrichment with EPA inhibited the ability of accessory cells to present antigen to murine helper T-cell clones. This effect was observed for two distinct helper T-cell clones, Th1 and Th2. We also examined the effects of EPA-TG emulsion on APC function. The direct addition of EPA-TG emulsion to a T-cell proliferation assay system suppressed APC function. The inhibition was proportional to the concentration of EPA-TG emulsion. Pretreatment of splenocytes with EPA-TG emulsion resulted in inhibition of APC function. Inhibition of antigen presentation by dietary supplementation with EPA might depress immune reactivity.

Docosahexaenoic and eicosapentaenoic acids in plasma phospholipids are divergently associated with high density lipoprotein in humans.

Abstract: The effect of fish oil rich in eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids on serum lipoprotein concentrations is not clear, and it is not known whether EPA and DHA are similarly related to serum lipid or lipoprotein levels. We conducted a randomized, 10-week, dietary supplementation trial in which the effects of 6 g per day of 85% EPA and DHA were compared with 6 g per day of corn oil in 156 men and women. Multivariate analyses were used to assess independent relations between plasma phospholipid EPA and DHA and serum lipoprotein levels. In the fish oil group triglycerides fell 21% (p less than 0.001) and high density lipoprotein cholesterol (HDL-C) rose 3.8% (p less than 0.05). In the corn oil group triglycerides did not change, but HDL-C rose 6.1% (p less than 0.01). Compared with fish oil, apolipoprotein A-I (apo A-I) rose 5.1% after corn oil intake (p less than 0.05). Plasma EPA and DHA levels rose after fish oil intake and fell after corn oil intake (all p less than 0.001). The change (delta) in EPA was inversely correlated with delta triglycerides (p = 0.035) and positively correlated with delta HDL-C and delta apo A-I (both p less than 0.001) in the multivariate analyses. In contrast, delta DHA was not correlated with delta triglycerides but was inversely correlated with delta HDL-C and delta apo A-I (both p less than 0.001). Standardizing for DHA removed the difference in apo A-I levels between groups. This study suggests that EPA and DHA are divergently associated with HDL, possibly through different mechanisms.